CN111830053A - Transmitted light inspection apparatus and transmitted light inspection method for inspecting containers - Google Patents
Transmitted light inspection apparatus and transmitted light inspection method for inspecting containers Download PDFInfo
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- 238000007689 inspection Methods 0.000 title claims abstract description 67
- 238000000034 method Methods 0.000 title claims abstract description 17
- 230000003595 spectral effect Effects 0.000 claims abstract description 56
- 238000005286 illumination Methods 0.000 claims abstract description 23
- 235000013361 beverage Nutrition 0.000 claims abstract description 11
- 239000011159 matrix material Substances 0.000 claims description 109
- 230000010287 polarization Effects 0.000 claims description 75
- 230000005540 biological transmission Effects 0.000 claims description 4
- 238000002360 preparation method Methods 0.000 claims 2
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- 238000001429 visible spectrum Methods 0.000 description 4
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- 238000003672 processing method Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000000071 blow moulding Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000009969 flowable effect Effects 0.000 description 1
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- 239000002674 ointment Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/90—Investigating the presence of flaws or contamination in a container or its contents
- G01N21/9081—Inspection especially designed for plastic containers, e.g. preforms
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/90—Investigating the presence of flaws or contamination in a container or its contents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
- B07C5/34—Sorting according to other particular properties
- B07C5/3404—Sorting according to other particular properties according to properties of containers or receptacles, e.g. rigidity, leaks, fill-level
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
- B07C5/34—Sorting according to other particular properties
- B07C5/342—Sorting according to other particular properties according to optical properties, e.g. colour
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/21—Polarisation-affecting properties
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/21—Polarisation-affecting properties
- G01N21/211—Ellipsometry
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/21—Polarisation-affecting properties
- G01N2021/216—Polarisation-affecting properties using circular polarised light
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- General Health & Medical Sciences (AREA)
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- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The present invention relates to a transmitted light inspection apparatus and a transmitted light inspection method for inspecting a container. A light-transmitting inspection device (1) for inspecting containers (2), such as preforms and/or beverage containers, has: a transport means (3) for transporting the containers (2), and at least one inspection station (4, 5) attached to the transport means (3) for transilluminating the containers (2) with polarized light (L), wherein the at least one inspection station (4, 5) comprises an illumination device (4) having a light source (4.1) and having a rear polarizer (4.2) and a camera system (5) having at least one analyzer (5.M, 5.F1, 5.F2, 5.T), wherein the illumination device (4) is designed to emit polarized light (L) having at least two different spectral ranges, and wherein the camera system (5) is designed to detect the at least two different spectral ranges of the polarized light (L) separately from one another.
Description
Technical Field
The present invention relates to a light inspection apparatus and a light inspection method for inspecting containers, such as preforms and/or beverage containers, having the features described in the preamble of claims 1 and 10.
Background
For example, WO 2017/008944 a1 discloses an inspection apparatus for preforms comprising a first camera for mouth inspection and a second camera for bottom inspection, wherein the illumination unit is configured to illuminate both the mouth region with incident light and the bottom region with transmitted light.
WO 2005/01983 a1 discloses a method and system for identifying a core blocking material in a container preform.
DE 202013100834U 1 discloses a device for detecting dirt on containers, in which a polarizer is configured such that the light emitted by an illumination device is circularly or elliptically polarized, and the containers are detected by means of two cameras, the analyzers of which are preceded by different directions of rotational polarization, in order to identify dirt behind the label particularly well. However, such configurations are complex and expensive.
Such transmitted light inspection devices and methods are commonly used in beverage processing facilities to inspect containers, such as preforms or beverage containers, in a production line and discard them when problems arise in the process. For example, there may be broken containers with material defects, such as inclusions, bubbles, scratches, pits, and/or scratches.
A transmitted light inspection apparatus typically includes a transporter for transporting containers and at least one inspection station attached to the transporter for transilluminating the containers with polarized light. During the inspection, the container is guided between an illumination device with a rear polarizer and a camera system with a front analyzer, and is thus transilluminated with polarized light and detected with the camera system.
Tension in the material often produces stress birefringence effects that can be identified when transilluminated with polarized light. Material defects are related to locally varying portions of the material tension and thus can be detected when transilluminated with polarized light and then identified in the camera image using well known image processing algorithms.
In rare cases, however, it is also possible that material defects cannot be reliably identified.
Disclosure of Invention
It is therefore an object of the present invention to provide a transmitted light inspection apparatus and a transmitted light inspection method with which material defects in containers can be identified more reliably in a container processing facility.
In order to solve the above-mentioned object, the invention proposes a transmitted light inspection apparatus having the features described in claim 1. Advantageous embodiments are described in the dependent claims.
Extensive studies by the applicant have shown that material defects can be identified optimally if the illumination device emits polarized light in a manner having at least two different spectral ranges, which are detected separately from one another by the camera system. It has been found that the material properties of the stress refraction exhibit different intensities in different spectral ranges, whereby defects can be reproduced in the detected camera image with different contrasts, so that defects can be identified more reliably.
The transmitted light inspection apparatus may be disposed in a beverage processing facility. The transmitted light inspection apparatus may also be arranged in a facility for manufacturing containers. The transmitted light inspection apparatus may be post-positioned in a pre-selector to sort containers identified by at least one inspection station as being defective in one or more materials. The sorted containers may be cleaned or recycled. Furthermore, the preselector may be configured to feed the material defect free containers to a container processing machine, such as a filling machine.
The container may be, in particular, a preform and/or a beverage container. It may preferably be a plastic container, but glass containers are also contemplated. The preforms can be provided for producing finished plastic containers from the preforms in a production step, for example by means of a stretch blow molding machine. The preform can, for example, be configured as a test tube and comprise the finished container mouth. The beverage container may preferably be arranged for containing beverages, hygiene products, ointments, chemical, biological and/or pharmaceutical products. It will generally be possible to arrange the beverage container for any flowable or fillable medium.
The inspection station may be configured to detect material defects. Material defects may include, for example, undesirable tension, material thickness fluctuations, inclusions, bubbles, scratches, pits, and/or scratches.
The transport device can preferably be designed as a linear transport device, wherein the illumination device with the polarizer is arranged on one side and the camera system with the at least one analyzer is arranged on the opposite side. It is also conceivable that the transport device is designed as a carousel, by means of which the containers are transported between the illumination device with the polarizer and the camera system with the at least one analyzer.
The illumination means may comprise a light source, a lens, a diffuser and/or a diaphragm. The light source as a lighting means may comprise an incandescent lamp, a gas discharge lamp, a fluorescent tube and/or an LED. The light source is preferably formed by at least one circuit board with a matrix arrangement of LEDs. It is envisaged that the lighting device comprises LEDs having at least two different light colors, so as to emit at least two different spectral ranges.
The light source may emit at least two different spectral ranges in the visible spectrum and/or in the infrared spectrum. The visible spectrum may be in the wavelength range of 380nm to 780nm, preferably 440nm to 650nm, and/or the infrared spectrum may be in the wavelength range of 780nm to 3 μm, preferably 800nm to 1 μm. The at least two different spectral ranges may cover different ranges of the visible spectrum and/or the infrared spectrum, respectively. It is conceivable that at least two different spectral ranges are directly connected to each other. In other words, it is conceivable that the lighting device emits polarized light within a continuous spectrum comprising at least two different spectral ranges. Alternatively, it is conceivable that at least two different spectral ranges are separated from each other by at least one bandgap. In both variants, at least two different spectral ranges are detected separately by the camera system. For example, one of the at least two different spectral ranges may comprise a yellow spectrum and the other may comprise a blue spectrum. In another example, one of the at least two different spectral ranges may comprise a red spectrum and the other may comprise a green spectrum. The at least two different spectral ranges may be, independently of each other, narrow-band or wide-band, respectively. For example, in the case of a monochromatic LED, at least one of the at least two different spectral ranges may be a monochromatic spectrum or a narrow-band spectrum, for example.
The polarizer may be arranged within the lighting device or in a light exit area of the lighting device. The polarizer and/or the analyzer may be formed at least in sections as a sheet or foil. The polarizer and/or analyzer may for example be a polarizing foil. The polarizer of the illumination device may preferably comprise a linear polarizing filter, a circular polarizing filter or an elliptical polarizing filter.
The camera system may include a camera and an objective lens. The camera may comprise a line sensor or a matrix sensor, such as a CCD sensor or a CMOS sensor. The camera system can be connected to an image processing unit via a data line in order to evaluate the camera image of the transilluminated container, in particular with regard to material defects. It is also conceivable to integrate the image processing unit into the camera system. It is conceivable that the camera system is configured to simultaneously detect at least two different spectral ranges of the polarized light separately from each other, for example by means of one or more color cameras and/or color filters. Alternatively, it is also conceivable that the camera system is configured to detect the at least two different spectral ranges of the polarized light successively and temporally separately, for example by sequential image acquisition.
The camera system may for example comprise a color camera in order to separately detect at least two different spectral ranges. The color camera may for example comprise a matrix sensor with a so-called bayer filter. Alternatively, it is also conceivable for the camera system to comprise a plurality of cameras, each having a matrix sensor, an objective lens and each having a different color filter.
It is conceivable for the mirror cabinet to be arranged in front of the camera system in order to detect a plurality of container sides of the containers adjacent to one another as image regions of the camera image.
The transmitted light inspection apparatus may comprise control means for controlling the illumination means and/or the camera system. The control device may further comprise an image processing unit for receiving camera images of the camera system and for evaluating the material defects. The control device may also be configured to control the transporter and/or detect a transport position of the container. It is envisaged that the control means comprises a digital processor (CPU), a memory unit, an interface unit, an input and/or output unit.
The camera system may be configured to separately detect at least two different polarization directions of the polarized light for at least one of the at least two different spectral ranges, in particular simultaneously. This can further improve the reliability of the inspection. The polarization directions detected by means of the at least one analyzer and camera system may comprise 0 ° and 90 ° or 0 °, 45 °, 90 ° and 135 °. In other words, the at least two different polarization directions can be respectively rotated by 90 ° or 45 ° relative to each other. The at least one analyzer may be at least one linear polarizing filter. It is also contemplated that the at least one analyzer includes an elliptical or circular polarizing filter. Mixtures of the above types of polarizing filters are also contemplated. In other words, the at least one analyzer may comprise any combination of linear polarizing filters, elliptical polarizing filters, and/or circular polarizing filters. The camera system may in particular be configured to detect at least two different spectral ranges and/or at least two different polarization directions simultaneously.
The camera system may comprise an objective lens and a matrix sensor, wherein the at least one analyzer is configured as a polarization analyzer matrix which is arranged between the objective lens and a photosensitive sensor element of the matrix sensor in order to detect at least two different polarization directions by means of the matrix sensor. The camera system can thus be constructed in a particularly simple manner, since two different polarization directions are detected for one spectral range with exactly one matrix sensor instead of with a plurality of matrix sensors.
The matrix sensor may comprise as an integrated element an analyzer configured as an analyzer matrix. This makes the construction of the mirror chamber system more compact and simple. It is conceivable that an analyzer configured as a matrix of analyzers is arranged between the microlens array and the photosensitive sensor elements of the matrix sensor. Thereby enabling the use of a particularly wide variety of objective lens types without affecting image quality. It is also conceivable, however, to arrange the analyzer in the form of an analyzer matrix directly in front of the microlens array of the matrix sensor.
The analyzer, which is embodied as a polarization analyzer matrix, comprises a plurality of polarizer elements arranged in a matrix, which are each assigned to one of the photosensitive sensor elements and are preferably oriented alternately in at least two, in particular exactly four, different polarization directions. The light-sensitive sensor elements of the matrix sensor are therefore each assigned a different polarizer element of the analyzer, so that particularly high-resolution imaging of the container is possible with a consideration of the polarization of each pixel. Each light-sensitive sensor element may correspond to a pixel in the camera image output by the matrix sensor, in particular wherein each light-sensitive sensor element is assigned a polarizer element of an analyzer. The polarizer elements arranged in a matrix can each be designed as a polarization filter, wherein they are arranged in a matrix in a twisted manner relative to one another, so that at least two different polarization directions are detected. The polarization directions are, for example, 0 ° and 90 ° or 0 °, 45 °, 90 ° and 135 °.
The polarizer elements arranged in a matrix can be grouped such that at least two, in particular four, adjacently arranged polarizer elements are each oriented in at least two, in particular four, different polarization directions and form a group. In this way, different polarization directions are detected alternately by the photosensitive sensor elements of the matrix sensor, so that a particularly high spatial resolution is obtained in the camera image, taking the polarization into account. It is conceivable that the groups themselves are arranged in a matrix on the matrix sensor. Thereby alternately detecting different linear polarization directions along the two axes of the matrix sensor.
The matrix sensor may for example be an image sensor of the Sony IMX250MZR type or the IMX250MYR type, in particular wherein an analyzer constructed as an analyzer matrix is arranged between the microlens array and the pixel array of the matrix sensor. However, it is also conceivable for the analyzer, which is designed as an analyzer matrix, to be arranged directly in front of the microlens array of the matrix sensor in the beam path of the camera system. It is also conceivable for the camera system to be constructed with filters for separately detecting different light wave lengths, in particular with at least one bayer filter or at least one pixel-by-pixel color filter, in order to detect different light wavelengths of the polarized light in addition to different polarization directions. This may be for example a Sony IMX250MYR type matrix sensor, which is able to detect color in addition to polarization.
Alternatively, it is also conceivable for the camera system to comprise at least two color cameras, each having an analyzer, an objective and a matrix sensor, wherein the analyzers of the at least two color cameras are configured or oriented in at least two different polarization directions. Thus, although more color cameras are required, containers can be detected spatially with higher resolution. It is envisaged that the analyzer comprises a linear or circular polarisation filter respectively. The linear polarization filter may be arranged torsionally so as to be able to detect the linear polarization directions at 0 ° and 90 ° or 0 °, 45 °, 90 ° and 135 °.
In a further alternative, it is also conceivable that the camera system comprises at least two color cameras with lenses and with matrix sensors, wherein the at least one analyzer comprises a polarization beam splitter in order to divide the at least two different polarization directions onto the at least two color cameras. The image fields can thus be superimposed by the two color cameras, respectively, so that the image perspectives in the respective camera images are similar or even identical. The assignment of the image area of the container in the camera image can thus be supported during the evaluation. The polarizing beamsplitter may be an optical element that transmits a first direction of linear polarization and reflects a second direction of linear polarization that is 90 ° twisted therewith.
Here, a color camera may refer to a camera with a line sensor or a matrix sensor, for example with a CCD sensor or a CMOS sensor, and with a bayer filter, in order to separate different spectral ranges. However, color cameras with color separation systems which divide different spectral ranges over a plurality of line sensors or matrix sensors are also conceivable. The color separation system may for example be a prism system with three different color filters.
The invention further provides a transmitted light inspection method for inspecting a container for a side wall, having the features described in claim 10. Advantageous embodiments of the invention are described in the dependent claims.
Extensive studies by the applicant have shown that material defects can be identified optimally if the illumination device emits polarized light in a manner having at least two different spectral ranges, which are detected separately from one another by the camera system. It has been found that the material properties of the stress refraction exhibit different intensities in different spectral ranges, so that defects can be reproduced in the detected camera image with different contrasts, so that defects can be identified more reliably.
The transmitted light inspection method in the sense of the present invention may comprise the features described above with reference to the transmitted light inspection apparatus, in particular the features according to any one of claims 1 to 9, individually or in any combination. It is conceivable that the transmitted light inspection method is performed by means of the above-described transmitted light inspection apparatus, in particular the transmitted light inspection apparatus according to any one of claims 1 to 9.
The at least one analyzer may divide the at least two different linear polarization directions as a polarization analyzer matrix after the objective lens and before the light-sensitive sensor elements of the matrix sensor in such a way that the at least two different polarization directions are detected in the camera image of the matrix sensor. The camera system can thus be constructed in a particularly simple manner, since at least two different polarization directions are detected by means of exactly one matrix sensor, rather than by means of a plurality of matrix sensors.
It is conceivable that a color filter matrix is associated with the analyzer, which is designed as an analyzer matrix, by means of which color filter matrix at least two different polarization directions of the polarized light are separated in each case for at least one of the at least two different spectral ranges. This allows at least two different spectral ranges and at least two different polarization directions to be detected separately with only one camera. The method can therefore be carried out with particularly simple components. It may for example be a color camera with a Sony IMX250MYR type image sensor.
Alternatively, it is also conceivable to detect at least two different polarization directions by at least two color cameras having a polarization analyzer, an objective lens, respectively, and a matrix sensor, respectively. This allows containers to be detected spatially with a higher resolution, although a plurality of color cameras are required.
Alternatively, it is also conceivable to detect at least two different polarization directions by at least two color cameras each having an objective and each having a matrix sensor, wherein the at least one analyzer comprises a polarization beam splitter, by means of which the two different polarization directions are divided onto the at least two color cameras. Whereby the image fields can be superimposed by two color cameras so that the image perspectives in the respective camera images are similar or even identical. This enables the assignment of the image region of the container in the camera image to be supported during the evaluation.
Drawings
Further features and advantages of the invention are explained in detail below with reference to exemplary embodiments shown in the drawings. Wherein:
FIG. 1 shows an embodiment of a transmission light inspection apparatus according to the invention in a side view;
FIG. 2 shows an exemplary detail view of a matrix sensor with analyzers configured as a matrix of analyzers and a matrix of color filters in a front view;
FIG. 3 shows, in a side view, another embodiment of a transmitted light inspection apparatus according to the present invention having two cameras, in front of which analyzers are arranged, respectively; and
FIG. 4 shows, in a side view, yet another embodiment of a transmitted light inspection apparatus according to the present invention having two cameras and a polarizing beamsplitter.
Detailed Description
Fig. 1 shows an embodiment of a transmission light inspection apparatus 1 according to the invention in a side view. The figure shows a transport 3 and inspection stations 4, 5 attached to it for transilluminating containers 2 with polarized light L. The container is here, for example, a preform made of plastic. However, other containers, such as PET bottles, are also conceivable.
The transport device 3 is designed as a linear transport device, for example, in order to transport the containers 2 between the illumination device 4 and the camera system 5. In this case, the containers 2 can preferably be transported continuously and continuously detected by the camera system 5.
The lighting device 4 comprises a light source 4.1 for emitting light in the visible spectrum and/or in the infrared spectrum. The light source 4.1 is constructed, for example, with a plurality of LEDs which emit a white spectrum, preferably in the wavelength range from 380nm to 780 nm. The white spectrum comprises at least two different spectral ranges, in particular continuously connected to each other or separated by a band gap, for example a red spectral range, a yellow spectral range, a green spectral range and/or a blue spectral range. The white spectrum may also comprise only two or even more different spectral ranges of the above mentioned spectral ranges. It is also conceivable that the light source 4.1 is configured with a plurality of LEDs emitting infrared light preferably in the wavelength range of 780nm to 3 μm.
Furthermore, a polarizer 4.2 is placed behind the light source 4.1, which polarizer is configured to linearly polarize the light spectrum emitted by the light source 4.1. The polarizer 4.2 linearly polarizes the unpolarized light from the light source 4.1 and thus emits it as polarized light L. But circular polarizers or elliptical polarizers are also conceivable.
It can also be seen that the camera system 5 comprises an objective 5.3, a polarization analyzer 5.M and a matrix sensor 5.2, wherein the polarization analyzer 5.M is configured as a polarization analyzer matrix arranged between the objective 5.3 and the photosensitive sensor elements 5.21 of the matrix sensor 5.2. At least two, in particular four, different polarization directions can thus be detected in the camera image of the matrix sensor 5.2. Furthermore, a color filter matrix 5.C is assigned to the analyzer 5.M in order to separately detect at least two different spectral ranges of the polarized light L. In addition, the analyzer 5.M configured as an analyzer matrix and the color filter matrix 5.C are configured as integrated elements of the matrix sensor 5.2. The matrix sensor 5.2 and the analyzer 5.M constructed as an analyzer matrix may for example be a Sony IMX250MYR type (color) image sensor. A more detailed structure of the matrix sensor 5.2 and the analyzer 5.M is further explained below with reference to fig. 2.
In this connection, it is also conceivable for the camera system 5 to comprise at least two cameras, each having a matrix sensor 5.2 and each having an analyzer 5.M, which is designed as an analyzer matrix, but not having a color filter matrix. Each of these cameras is then preceded by a color filter corresponding to a spectral range in order to separate at least two different spectral ranges. The matrix sensor 5.2 may for example be an image sensor of the Sony IMX250MZR type. In other words, one of two different spectral ranges is detected by means of the camera.
By means of the objective 5.3, the container 2 is imaged onto a matrix sensor 5.2 of the camera system 5 via a color filter matrix 5.C and an analyzer 5. M. Thus, by means of the camera system 5, the container 2 can be detected in a spatially resolved manner in at least two different polarization directions simultaneously.
It is also conceivable that a mirror cabinet (not specifically shown in the figures) is frontally arranged in the camera system 5. This enables a plurality of container sides to be imaged side by side as image fields in the camera system 5. By means of the mirror cabinet and the objective 5.3, for example, at least two views of the container 2 can be imaged side by side from different viewing angles onto the matrix sensor 5.2, so that detection takes place in the camera image.
A control device 6 is also shown, with which the illumination device 4 and the camera system 5 can be controlled. It is conceivable that the control means 6 comprise image processing means for evaluating camera images from the camera system 5. It is also conceivable that the control device 6 controls the illumination device 4, for example based on signals from the light barrier, so that the illumination device emits light pulses when the container 2 is positioned in front of the illumination device 4 within the field of view of the camera system 5.
An exemplary detail view of a matrix sensor 5.2 with an analyzer 5.M configured as an analyzer matrix and a color filter matrix 5.C is shown in fig. 2. A matrix sensor 5.2 can be seen, which is used as an image sensor in the mirror chamber system 5 shown in fig. 1.
The matrix sensor 5.2 corresponds to the conventional structure of a CMOS image sensor or a CCD image sensor, wherein the light sensitive sensor elements 5.21 are arranged in a matrix-like grid in order to receive a camera image. A hexagonal arrangement of the light-sensitive sensor elements 5.21 is also conceivable.
Furthermore, the photosensitive sensor element 5.21 is preceded by an analyzer 5.M configured as a matrix of analyzers, comprising a plurality of polarizer elements 5.M1 to 5.M4 arranged in a matrix. Here, the matrix of polarizer elements 5.M1 to 5.M4 corresponds to the position of the light-sensitive sensor element 5.21 of the matrix sensor 5.2. One of the light-sensitive sensor elements 5.21 is assigned a respective polarizer element 5.M1 to 5.M4, which, as can be seen in detail D, are oriented alternately in four different linear polarization directions. The polarizer elements 5.M1 to 5.M4 are arranged, for example, with polarization directions of 0 °, 45 °, 90 ° and 135 °, respectively. Alternatively, the polarizing elements can also be oriented in two different polarization directions. It is conceivable that an analyzer 5.M configured as an analyzer matrix is arranged between the microlens array and the photosensitive sensor elements 5.21 of the matrix sensor 5.2.
Furthermore, the polarizer elements 5.M1 to 5.M4 arranged in a matrix are grouped such that the respective four adjacently arranged polarizer elements 5.M1 to 5.M4 are oriented in four different linear polarization directions and form one of the groups GR、GG1、GG2、GB. These groups GR、GG1、GG2、GBLikewise in each case arranged in a matrix, wherein the color filter elements in the color filter matrix 5.C are each assigned to four adjacent polarizer elements 5.M1 to 5.M4 arranged in a square, in order to transmit one of the different spectral ranges to the four photosensor elements 5.21 located behind. Group GRAssigned red filter elements, group GG1、GG2Are assigned to green filter elements, respectively, and group GBThe blue filter element is assigned to detect the red spectral range, the green spectral range and the blue spectral range separately from one another, in each case by means of the photosensitive sensor element 5.21 of the rear matrix sensor 5.2. It may be a bayer filter, which is assigned as a color filter matrix 5.C to an analyzer 5.M, which is designed as an analyzer matrix.
Four linear polarization directions and three different spectral ranges can thus be detected in one camera image by means of the matrix sensor shown in fig. 2. The transmitted light inspection apparatus 1 shown in fig. 1 can therefore be constructed particularly simply with only one camera.
With the aid of the transmitted light inspection apparatus 1 shown in fig. 1 and 2, the containers 2 are transported using a transport 3 to inspection stations 4, 5 attached to the transport and transilluminated here with polarized light L. For this purpose, the initially unpolarized light from the light source 4.1 is linearly polarized, for example by means of a polarizer 4.2, and emitted as polarized light L. Upon transillumination, the polarization of the light is influenced by the material of the container 2 and/or material defects F, for example by being rotated under tension by stress birefringence effects or being absorbed in a specific direction. The transilluminated container 2 is detected by means of a camera system 5, which comprises a matrix sensor 5.2 and an analyzer 5M, which is designed as an analyzer matrix. Four different linear polarization directions are thereby detected simultaneously in one camera image of the camera system 5. Furthermore, the illumination device emits polarized light in at least two different spectral ranges, wherein the camera system detects the at least two different spectral ranges separately from one another. Depending on the arrangement and nature of the material defects F, they then appear darker in certain linear polarization directions and colors in the camera image than the remaining regions of the container 2, so that they can be identified using conventional image processing methods.
Fig. 3 shows a further exemplary embodiment of a transmission light inspection device 1 according to the invention in a side view, with two color cameras 5A, 5B, in front of which analyzers 5.F1, 5.F2 are arranged in each case. The embodiment shown in fig. 3 differs from that of fig. 1 only in the structure of the camera system 5. Accordingly, the features of the lighting device 4 and the transporter 3 of the embodiment in fig. 1 apply correspondingly to fig. 3 as well as to fig. 4 below.
It can be seen that the objective lenses 5.3 of the color cameras 5A, 5B are assigned analyzers 5.F1, 5.F2, respectively. Here, it is for example a linear polarization filter which is twisted about the axis of the objective 5.3 into different rotational positions such that they transmit different linear polarization directions, for example directions 0 ° and 90 °, respectively. One of the linear polarization directions can thus be detected by one of the color cameras 5A, 5B. Thus, although the structure is more complex, higher spatial resolution can be achieved in the camera image. The color camera may, for example, comprise a matrix sensor and a preceding bayer filter in order to separate the different spectral ranges.
A further embodiment of a transmitted light inspection apparatus 1 according to the invention is shown in fig. 4, having two color cameras 5A, 5B and a polarizing beam splitter 5. T. The embodiment in fig. 4 differs from the embodiment in fig. 3 only in the type of analyzer 5. T. Here, the two different linear polarization directions are not divided by a polarizing filter, but by the illustrated polarizing beam splitter 5.T onto the two color cameras 5A, 5B, whereby the image fields of the color cameras 5A, 5B can be superimposed such that the image perspectives in the respective camera images are similar or even identical. The assignment of the image region of the container 2 in the camera image can thus be supported during the evaluation.
With the aid of the transmission-light inspection apparatus 1 shown in fig. 3 and 4, the containers 2 are transported using a transport 3 to inspection stations 4, 5 attached to the transport and are transilluminated here with polarized light L. For this purpose, the initially unpolarized light from the light source 4.1 is linearly polarized, for example by means of a polarizer 4.2, and emitted as polarized light L. Upon transillumination, the polarization of the light is affected by the material and/or material defects F, for example by being rotated under tension by stress birefringence effects or being absorbed in a particular direction. The container 2 thus transilluminated is detected by means of two color cameras 5A, 5B in two different directions of linear polarization. For this purpose, the color cameras 5A, 5B are either preceded by polarization filters 5.F1, 5.F2 or preceded by a polarization beam splitter 5. T. In this way, in the two camera images of the camera system 5, respectively different linear polarization directions are detected simultaneously. Furthermore, the illumination device emits polarized light in at least two different spectral ranges, wherein the camera system with the color camera detects the at least two different spectral ranges separately from one another. Depending on the arrangement and nature of the material defects F, they appear darker in one of the camera images than in the remaining region of the container 2 for a certain linear polarization direction, so that they can be identified using conventional image processing methods.
In the embodiment of fig. 1-4, the camera system 5 and the at least one analyzer 5.M, 5.F1, 5.F2, 5.T are configured to recognize two different linear polarization directions simultaneously, thus enabling transmitted light inspection of containers 2 with polarized light even in high throughput container processing plants. Furthermore, the material defects F can be identified particularly reliably by detecting the spectral ranges separately from one another.
It goes without saying that the features described in the above embodiments are not limited to the above-described combinations of features, but can also be implemented individually or in any other combination.
Claims (14)
1. Transmitted light inspection apparatus (1) for inspecting containers (2), such as preforms and/or beverage containers, comprising:
-a conveyor (3) for conveying the containers (2); and
-at least one inspection station (4, 5) attached to the conveyor (3) for transilluminating the containers (2) with polarized light (L),
wherein the at least one inspection station (4, 5) comprises an illumination device (4) having a light source (4.1) and having a rear polarizer (4.2) and a camera system (5) having at least one analyzer (5.M, 5.F1, 5.F2, 5.T),
it is characterized in that the preparation method is characterized in that,
the illumination device (4) is configured to emit polarized light (L) having at least two different spectral ranges; and is
The camera system (5) is configured to detect the at least two different spectral ranges of the polarized light (L) separately from each other.
2. The transmitted light inspection apparatus (1) according to claim 1, wherein the camera system (5) is configured to separately detect at least two different polarization directions of the polarized light (L) for at least one of the at least two different spectral ranges.
3. The transmitted light inspection apparatus (1) according to claim 2, wherein the camera system (5) comprises an objective lens (5.3) and a matrix sensor (5.2), and wherein the at least one analyzer (5.M) is configured as a matrix of analyzers arranged between the objective lens (5.3) and photosensitive sensor elements (5.21) of the matrix sensor (5.2) for simultaneously detecting the at least two different polarization directions by means of the matrix sensor (5.2).
4. The transmission light inspection apparatus (1) according to claim 3, wherein the matrix sensor (5.2) comprises as an integrated element an analyzer (5.M) configured as an analyzer matrix.
5. The transmission-light inspection device (1) according to claim 3 or 4, wherein the analyzer (5.M) configured as an analyzer matrix comprises a plurality of polarizer elements (5. M1-5. M4) arranged in a matrix, which are respectively assigned to one of the photosensor elements (5.21) and are preferably alternately oriented into at least two, in particular exactly four, different polarization directions.
6. The transmitted light inspection apparatus (1) of claim 5, wherein the polarizer elements (5. M1-5. M4) arranged in a matrix are grouped such that at least two, in particular exactly four, adjacently arranged polarizer elements (5. M1-5. M4) are respectively oriented into at least two, in particular exactly four, different polarization directions and form a group (G)R、GG1、GG2、GB)。
7. The transmitted light inspection apparatus (1) according to one of claims 3 to 6, wherein a color filter matrix (5.C) is assigned to the analyzer (5.M) configured as an analyzer matrix in order to separately detect at least two different polarization directions of the polarized light (L) for the at least two different spectral ranges, respectively.
8. The transmitted light inspection apparatus (1) according to claim 2, wherein the camera system (5) comprises at least two color cameras (5A, 5B) with analyzers (5.F1, 5.F2), respectively, an objective lens (5.3) and with a matrix sensor (5.2), and wherein the analyzers (5.F1, 5.F2) of the at least two color cameras (5A, 5B) are configured or oriented for the at least two different polarization directions.
9. The transmitted light inspection apparatus (1) according to claim 2, wherein the camera system (5) comprises at least two color cameras (5A, 5B) with objective lenses (5.3) and with matrix sensors (5.2), and wherein the at least one analyzer (5.T) comprises a polarizing beam splitter in order to divide the at least two different polarization directions onto the at least two color cameras (5A, 5B).
10. Transmitted light inspection method for inspecting containers (2), such as preforms and/or beverage containers, wherein the containers (2) are transported by means of a conveyor (3) to at least one inspection station (4, 5) attached to the conveyor and transilluminated by means of polarized light (L) by means of the at least one inspection station (4, 5), wherein the at least one inspection station (4, 5) comprises an illumination device (4) with a light source (4.1) and with a rear polarizer (4.2), which emits polarized light (L), and wherein the at least one inspection station (4, 5) comprises a camera system (5) with at least one analyzer (5.M, 5.F1, 5.F2, 5.T), by means of which the transilluminated containers (2) are detected,
it is characterized in that the preparation method is characterized in that,
the illumination device (4) emits polarized light (L) in at least two different spectral ranges; and is
The camera system (5) detects at least two different spectral ranges of the polarized light (L) separately from each other.
11. The transmitted light inspection method according to claim 10, wherein the at least one analyzer (5.M) divides at least two different polarization directions as an analyzer matrix behind the objective (5.3) and in front of the photosensitive sensor elements (5.21) of the matrix sensor (5.2), such that the at least two different polarization directions are detected in the camera image of the matrix sensor (5.2).
12. The transmitted light inspection method according to claim 11, wherein a color filter matrix (5.C) is assigned to the analyzer (5.M) configured as an analyzer matrix, by means of which at least two different polarization directions of the polarized light (L) are separated for at least one of the at least two different spectral ranges, respectively.
13. The transmitted light inspection method according to claim 10, wherein at least two different polarization directions are detected by at least two color cameras (5A, 5B) having analyzers (5.F1, 5.F2), respectively, objective lenses (5.3), and having matrix sensors (5.2), respectively.
14. The transmitted light inspection method according to claim 10, wherein at least two different polarization directions are detected by at least two color cameras (5A, 5B) each having an objective lens (5.3) and each having a matrix sensor (5.2), and wherein the at least one analyzer (5.T1) comprises a polarizing beam splitter by means of which the two different polarization directions are divided onto the at least two color cameras (5A, 5B).
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| DE102019205654.7 | 2019-04-18 | ||
| DE102019205654.7A DE102019205654A1 (en) | 2019-04-18 | 2019-04-18 | Transmitted light inspection device and method for inspecting containers |
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